US President Donald Trump has announced a 25% tariff on all steel and aluminium imports into the United States, eliminating all exceptions and exemptions, raising concerns for exporters, including South Korea.

Trump signed two proclamations formalizing the tariffs and confirmed plans to announce “reciprocal” tariffs within the next two days—duties on U.S. imports designed to match the tariff rates imposed by other countries on U.S. exports, according to Yonhap news agency.

During his first term, Trump had imposed a 25% tariff on steel imports and a 10% tariff on aluminium imports, citing national security concerns. The new measures will remove all duty-free quotas and exemptions for U.S. trading partners while raising the aluminium tariff to 25%. The tariffs will take effect on March 4.

“Today, I am simplifying our tariffs on steel and aluminium so that everyone can understand exactly what it means. It’s 25% without exceptions or exemptions, and that’s all countries, no matter where it comes from,” Trump told reporters as he signed the proclamations.

“If it’s made in the United States, there is no tariff. All you have to do is make it in the United States. We don’t need it from another country,” he added.

Announcing what he described as “massive” tariffs, Trump argued that the U.S. was “being pummelled by both friend and foe alike.”

“Our nation requires steel and aluminium to be made in America, not in foreign lands. We need to create in order to protect our country’s future resurgence of U.S. manufacturing and production, the likes of which have not been seen for many decades,” he said.

“It’s time for our great industries to come back to America … This is the first of many.”

When asked about possible retaliation from other countries, Trump said he was not concerned.

“If they retaliate, as I said, it’s reciprocal,” he said. “If they raise it a little bit, then we raise it automatically. So I don’t think it helps for them to retaliate.”

Trump also warned that his administration is considering tariffs on other key industries, including cars, semiconductors, and pharmaceuticals.

“Cars is going to be a very big one and a very important one, and America is going to be stronger than it ever was before,” he said.

Trump has already imposed a 10% tariff on all Chinese goods entering the U.S. and has temporarily paused the imposition of a 25% tariff on Canada and Mexico after both countries agreed to increase efforts to combat drug trafficking at their borders with the U.S.